There is known in the patent literature and on the marketplace a great variety of solar water heaters. Most of the water heaters which have enjoyed wide commercial acceptance comprise a flat plate collector through which water circulates for heating thereof. The heated water is stored in a tank.
Solar energy concentrators are also known. Examples of such concentrators are described in U.S. Pat. Nos. 4,162,824; 4,141,340; 4,069,812; 4,154,219; 4,056,094; 4,045,246; 4,024,852; and 4,003,364 and in German Offenlegungsschrift No. 2,827,708.